(1) Field of the Invention
This invention relates to an actuator unit with a housing that includes receptacles for a step-down gear unit and for a miniature electric motor, wherein the seating for the motor is connected to a terminal cover.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
An actuator unit of the type in question that serves as a drive for a piston of a drug-administering device with which slow, finely dosed drug dispensing is achieved, is known from U.S. 2011/0166512 A1. The seating for the miniature electric motor is designed here as a snap-fit connection that connects the terminal cover and the housing. This snap-fit connection requires very fine tolerances to limit the gap between the electric motor and the housing. Since the step-down gear unit is provided with a very fine gearing due to its small size and high reduction ratio, and since the miniature electric motor is a mass-produced item with a relatively large outer dimensional tolerance, the gearing of the step-down gear unit between a motor pinion and a gear wheel may disengage if the combination of parts is unfavorable, rendering the device unusable.
It is therefore the object of the present invention to provide a secure gap-free seating of the miniature electric motor of an actuator unit of the type in question as well as simple assembly and manufacture of the components used and high cost-effectiveness.